The purpose of this project is to develop a capsule to serve as an aid to in situ implantation of multiple tissue fragments into the fourth ventricle of rats for the study of neuronal growth and, ultimately, to reconstruction of severed neurological circuits. The capsule shall further serve as a mechanical constraint to maintain the tissue fragments in registration and in close juxtaposition while at the same time providing for angiogenesis from the overlying cerebellum. Various polymeric capsules of one millimeter diameter were developed having a range of dissolution characteristics based on methyl cellulose (demethyl ether) and methyl cellulose crosslinked with polyfunctional resins combined with crosslinked and non-crosslinked collagen. The capsules exhibited sufficient initial rigidity for ease of loading of the tissue fragments and insertion into the fourth ventricle, yet immediately became soft in cerebral fluid. Only materials with a proven history of biocompatibility were used. Dissolution times could be varied from 30 minutes to 8 hours in increments of 30 minutes depending upon the degree of crosslinking selected. The presence of the collagen added a plasticizing effect to the polymer system and provided a pseudo-fibrous network once the polymer dissolved. This network remains for extended periods and may be beneficial in supporting and confining the tissue fragments beyond the initial stages of growth. Preliminary studies showed the capsules to be tolerated by the animals and some evidence that conditions in the fourth ventricle are suitable for neuronal growth.